Strange bug with the -O2-for-C option

[Alain Cremieux]

Hi,
I encountered a strange and potentially dangerous bug trying to test
optimization.
I was trying to optimize the execution time of a canny edge detection
program coming from the nofib suite. What is happening is not what I
expected :
1) compiled with -O2, the image (edges) is correctly created
2) compiled with -O2 -O2-for-C, the image is completely black.
My environment : Linux with RedHat 7.1, GHC 5.00.2 compiled with itself
I have a test set for anyone interested in reproducing the bug,
Alain